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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./OL_SDK/include-openlayers-local.js"></script>
    <script src="./libs/gaode.js"></script>
</head>

<body>
    <div id="map">
    </div>
    <script>
        var map = new ol.Map({
            target: "map",
            layers: [gaode],
            view: new ol.View({
                projection: 'EPSG:4326',
                center: [114.30, 30.50],
                zoom: 4
            })
        })
        /* 创建画布 */
        const source = new ol.source.Vector({

        })
        const layer = new ol.layer.Vector({
            source
        })
        map.addLayer(layer);
        /* 创建画笔 */
        /* 正方形是基于圆构建的 */
        let draw = new ol.interaction.Draw({
            source: source,
            // 绘制的类型
            type: 'LineString',
            geometryFunction: function (coordinates, geometry) {
                if (!geometry) {
                    //多边形
                    geometry = new ol.geom.Polygon(null)
                }
                var start = coordinates[0]
                var end = coordinates[1]
                geometry.setCoordinates([
                    [start, [start[0], end[1]], end, [end[0], start[1]], start],
                ])
                return geometry
            },
            maxPoints: 2
        })
        /* 激活画笔  */
        map.addInteraction(draw);
    </script>
</body>

</html>